How did corporations and businesses transform the Sherman Antitrust act into a tool for their own benefits?

The Sherman Antitrust Act's purpose was to restrain various monopolies that had been created by businesses. In order to do so, the Act intended to place restrictions on these large groups. However, the corporations used this Act for their own benefit by placing restrictions on Labor Unions. In turn, the Labor Unions became upset because this act hurt them by restricting means of trade.